1. Field of the Invention
The subject invention relates generally to a heat exchanger and method of fabricating the same, and, more specifically, to a heat exchanger of the type including a plurality of refrigerant tubes extending between an inlet header and an outlet for transferring refrigerant from the inlet header to the outlet header and including a refrigerant conduit disposed in at least one of the headers for uniformly distributing the refrigerant.
2. Description of the Prior Art
Due to their high performance, automotive style brazed heat exchangers are being developed for residential air conditioning and heat pump applications. Automotive heat exchangers typically utilize a pair of headers with refrigerant tubes defining fluid passages to interconnect the headers. Residential heat exchangers are typically larger than automotive heat exchangers and generally require headers that are two to five times longer than the typical automotive heat exchangers. In such heat exchangers, uniform refrigerant distribution is necessary for optimal performance. To improve refrigerant distribution, refrigerant conduits can be disposed in the headers. An example of such a heat exchanger is disclosed in U.S. Pat. No. 1,684,083 to S. C. Bloom.
The Bloom patent discloses a first header being at least in part generally cylindrical in cross-section to define a first cavity extending parallel to a first header axis between a pair of first header end portions. A second header defining a second cavity extends along a second header axis between a pair of second header end portions. A plurality of refrigerant tubes each defining a fluid passage extends transversely to the header axes between the headers. The fluid passages of the refrigerant tubes are in fluid communication with the cavities for transferring refrigerant from one of the headers to the other of the headers. A refrigerant conduit having a conduit cross-section being circular is disposed in each of the cavities extending axially along the header axes parallel to the headers. The refrigerant conduits include a plurality of orifices in fluid communication with the associated cavities for transferring refrigerant between the refrigerant conduits and the associated cavities. One of the headers is an inlet header for receiving liquid refrigerant and the other of the headers is an outlet header for outputting refrigerant vapor. The refrigerant conduit disposed in the inlet header insures a uniform and even distribution of the refrigerant throughout the inlet header while the refrigerant conduit disposed in the outlet header insures only dry gas is withdrawn from the outlet header via the refrigerant conduit by a pump.
A heat exchanger as disclosed by the Bloom patent is typically made by puncturing a generally cylindrical first header defining a first cavity and a generally cylindrical second header defining a second cavity in predetermined spaced intervals axially along each header to define a plurality of header slots spaced axially along each header. A plurality of orifices is produced in a generally cylindrical refrigerant conduit, and the refrigerant conduit is inserted into the first cavity of the first header. The first and second headers are then placed in a stacker headering station fixture, and the headers are pressed onto a plurality of refrigerant tubes each defining a fluid passage to fluidly communicate the cavities of the headers. The refrigerant tubes typically extend through the header slots and into the cavities of the headers.
The increasing length of residential heat exchangers have created both manufacturing and performance problems with such heat exchangers as disclosed by the prior art. The increasing length has made it more difficult to insert a refrigerant conduit into a header without damaging the refrigerant tubes or the refrigerant conduit. Additionally, the increasing length has produced increasing problems with refrigerant maldistribution. Refrigerant maldistribution in a heat exchanger can be caused by both inlet maldistribution as well as the longitudinal pressure drop of the refrigerant conduit. Accordingly, there remains a need for an improved heat exchanger which is easier to manufacture and which provides for more uniform refrigerant distribution.